An accessory attachment system comprising a fastening key having an accessory retention cap, a stem extending from the retention cap, and at least one bit extending laterally from a distal end of the stem. The stem configured to be inserted through a key aperture in an accessory to be attached to the vehicle. The system includes a locking bracket connectable to the vehicle adjacent an accessory portal provided in the vehicle. The locking bracket comprises a base plate, a keyhole disposed through the base plate, and at least one inclined securing structure disposed along a circumference of the keyhole. Each securing structure comprises a ramp and a detent. The keyhole is configured to receive the stem distal end and bit(s) therethrough, and each securing structure is configured to engage the bit(s) and interlock the fastening key with the locking bracket upon rotation of the key.